Prismatic device.



H. JACOB & O. VON HOPE.

PBISMATIO DEVICE.

APPLICATION FILED we. a, 1909.

Patented Feb. 3, 1914.

Winesses:

M. W M.

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HEINRICH JACOB, OF STEGLITZ, NEAR BERLIN, AND CHRISTIAN VON HOFE, 0FWIL- MERSDORF, NEAR BERLIN, GERMANY, ASSIGNORS TO THE FIRM 0F OP'IISGHEANSTALT C. P. GOERZ AKTIENGESELLSCHAFT, OF FRIEDENAU, NEAR BERLZN,

GERMANY.

PRISMATIO DEVICE.

Specification of Letters Patent.

Patented Feb. 3,1914.

Application filed August 6, 1909. Serial No. 511,512.

To all whom it may concern.-

Be it known that we, Hmnnion Jl-xcon, a citizen of the German Empire,and resident of Steglitz, near Berlin, Germany, and CHRISTIAN VON Horn,a citizen of the German Empire, residing at 2st Hildegardstrasse,WVilmersdorf, near Berlin, Germany, have invented certain new and usefulImprovements in Prismatic Devices Particularly Adapted for Use inBase-Line Telem-' eters, of which the following is a specifica- Ourinvention relates to prismatic devices, particularly adapted to be usedin base line telemeters, that is to say to telemeters provided withoptical means for obtaining images ofobjects from the ends of a baseline, and with means for adjusting said images with relation to eachother and more particularly to those classes of base line telemeterswhich show the images of the distant objects positioned above and belowa horizontal line of division in the field of view of the observer, suchtelemeters being known as coincidence and as invert telemeters. Theoptical means of such instruments comprise an image uniting prism deviceperforming the function ofnniting the images produced from the ends orthe base line so that same are positioned above and below a line ofdivision as stated.

Now our invention consists in an improved image uniting prism devicewhereby the line of division in the field of view appears clear andsharp in its whole length. The improved image uniting prism deviceherein described comprises two prisms, one of which is a rhombohedraiprism, and tile other of which has a surface forming a continuation ofone of the surfaces of the rhomhoid and has another surface contactingwith a. further surface of the rhomboid, there being between theso-contacting surfaces of the two prisms, a reflecting layer having asharp limiting edge parallel to the line of demarcation between thosesurfaces of light coming from the two objectives of that telemeter.

An embodiment of the invention is illus trated on the annexed drawingwhich shows a telemeter with an image uniting prism device having a lineof image division in the field of view arranged in accordance with theinvention, said image uniting prism dc vice being in a perspectiveview-whereas the other optical elements of the telemeter are 'lonlydiagrammatically indicated in dotted mes.

The two objectives of the telemeter are designated 1, 2, j the referencenumeral 3. The base line of the instrument is designated 4: andpositioned intermediate the axes of the two obj ectives which are shownas having the same distances from the base line. The image uniting prismdevice consists of a rhombo hedral prism 5 contacting with a furtherprism 6 having a polished surface lying in a plane with one of the twosurfaces of the rhombohedral prism which intersect the contact surface.The contact surface of the prisms 5, 6 is partly provided with arefiecting'layer 7 having a limiting edge 8' forming the line of imagedivision in the field of view.

9 and 10 are two prisms with roof surfaces arranged for throwing therays coming from the objectives 1, 2 into the prism combination 5, 6.

The usual pentaprisms which reflect the rays coming from the distantobject looked at into the objectives are designated 11, 12.

The adjusting means of the instrument which maybe of any known orconvenientkind are not illustrated on the drawing in order to avoicomplication.

-As clearly i lustrated in the drawing the limiting edge 8 of thereflecting layer in the contact surface of the prismso, 6 is so ar-'ranged that the same is parallel to the plane of the measuring trianglethat isto say to] the plane of the triangle having its base.

prisms 11, 12 and its point'coinciding with. the distant object uponwhich the instrument is directed and that said edge 8 is at the sametime at right angles to the axis of the rays penetratingthrough the,prism combination 5, 6. It results fromthis arrange ment that if onepoint of the said line of .1 0 line coinciding With'line 4 between penta5 thereof, said prisms having each another surface angularly related tothe first mentioned surface of that pr1sm,,the said angularly relatedsurface of the one prism being in contact with the said angularlyrelated surface of the other prism, one of said angularly-relatcd prismsurfaces having a reflecting layer covering a portion only of thatsurface, the limiting edge of such reflectfing layer being parallel tothe line of demarcation between those surfaces of the prisms which arecontinuations one of another.

2. A prismatic device comprising a rhom- I bohedral prism and a secondprism, one surface of the second prism being in the same plane with asurface of the rhomboid, and forming a continuation thereof, anothersurface of said second prism being in contact with a surface of therhombohedral prism which is angularly related to the first mentionedsurface of that rhombohedral prism,

- Losses?- such angularly related surface of the rhombohedral prismbeing provided with a refleeting layer covering a portion only of suchsurface of said rhombohedra prism and having a limiting edge parallelwith the line of demarcation between the two surfaces of the said prismswhich are continuations of one another. 3. A prismatic deviceCOIl'lPIlSlIlg 111' combination a rhombohedral prism and a second prism,one surface of said second prism being in the same plane with one of thesurfaces of'the rhombohedral prism, and forming a continuation of suchsurface, another surface of said second prism being in contact with asurface of such rhombohedral prism which is angularly related to thefirst mentioned surface of such rhombohedral prism, a reflecting layerbeing provided between the said contacting surfaces of the two prisms,said reflecting layer coveringa portion only of the said contactingsurfaces of the two prisms and having a limiting edge parallel :to theline of demarcation between the first mentioned surfaces oflsaid prisms.

In testimony whereof we have signed this specification in the presenceof two subscril .1ng witnesses.

HEINRICH JACOB. CHRISTIAN VON HOFE. Witnesses:

HENRY HASPER, ARTHUR SoHRononR.

